Methods for the model-based control of an SCR catalytic converter of an internal combustion engine are known from the publications DE 10 347 130 A1, DE 10 347 131 A1 and DE 10 347 132 A1, wherein the respectively used dynamic model considers the NH3 loading of the SCR catalytic converter. A modelled NOx value of the dynamic model will be adjusted continuously by means of an NOx value measured by an NOx sensor arranged downstream of the SCR catalytic converter.
Dynamic filling level models for SCR control are based on a model of the SCR catalytic converter which models the current NH3 loading of the catalytic converter on the basis of mass balances. As a result of imprecisions in the sensor and actuator systems, this modelled NH3 loading can drift away from the real value during operation, which is why the modelled NH3 loading needs to be adjusted to the real loading in specific intervals.